Agender means that that person has no gender. It's not exactly a lack of expression, but more that they simply have no gender. It's also not that agender people hate genders/the concept of gender, it's again just that they simply wish to have no gender. An agender person may have no problem with behaving more masculine or feminine, while others may prefer to behave in a more androgynous manner. It all depends on their personal preference.